It is quite common for electronic circuitry to have a reset function. In this way, when power is first applied to the circuitry, the reset function can be employed to set the circuitry to a predetermined reset state. Frequently, the reset function may be activated through hardware, or through software, at times other than power-up of the circuitry. In the former case, the reset function is activated by applying a reset signal to the circuitry to be reset. In the latter case, a software command is provided that forces a reset signal to be generated. Regardless of how the reset function is activated, the value of being able to reset circuitry to a predetermined reset state is well known to those of ordinary skill in the art.
It is also well known in the art that there is utility to providing a "sleep" function to electronic circuitry. When a sleep mode is entered, typically by the application of a sleep command, most, if not all, circuitry is placed in a mode where the circuitry does not draw power. Later, when the sleep mode is ended, the electronic circuitry returns to the state the circuitry had upon entering the sleep mode.
The sleep mode permits power consumption to be eliminated, or at least significantly reduced, when the circuitry is in the sleep mode. Exiting from the sleep mode differs from resetting because the circuitry will only return to the reset state when the sleep mode ends if that was the state in which the circuitry resided upon entering the sleep state. More frequently, the electronic circuitry will be in some state other than the initial state when entering the sleep mode.